CO2 lasers are one of standards for laser processing such as cutting or drilling because high power of kW level is available, and its wavelength of 10 μm is absorbed for many materials regardless of metals and non-metals. However, this wavelength makes it difficult to reduce the spot diameter. High-power 5 μm laser by second-harmonic generation (SHG) of CO2 lasers would then realize more sophisticated laser processing with smaller spot sizes.